Spodoptera litura (F.) is an obnoxious cosmopolitan pest that causes serious damage to different economic crops. Entomopathogenic nematodes (EPN) have the potential to control the S. litura larvae. Fifteen EPN isolates were screened, and Steinernema sp. 64-2, four isolates of S. carpocapsae (Weiser), S. longicaudum (Shen & Wang) X-7, and two isolates of H. indica (Poinar, Karunaka & David) were found to cause higher mortality of the second, third, and fourth instars of S. litura than the other tested isolates, with larval mortality rates > 90% after 48 h of exposure. An exposure rate of 12.5 infective juveniles per larva was enough for S. carpocapsae A24, All, and G-R3a-2 and S. longicaudum X-7 to cause 100% mortality of the second instar, and for S. longicaudum X-7 and H. indica 212-2 to cause 100% mortality of the third instar. Five EPN isolates were tested on their virulence at different temperatures and found that all the five EPN isolates performed well against the S. litura larvae at 25 and 30°C, but were not active at 10 and 15°C. Two S. carpocapsae isolates (All and Mex) were virulent against the S. litura larvae at lower temperatures. The five tested EPN isolates were also found to have the ability to infect and kill the pupae of S. litura in the laboratory. The present study further proves that EPN are effective at controlling S. litura, which may partially substitute the use of chemical insecticides, thus reduce the overuse of chemical insecticides.

Summary The biological and biocontrol traits of two entomopathogenic nematode isolates, Steinernema pakistanense 94-1 (Sp94-1) and Heterorhabditis indica 212-2 (Hi212-2), were evaluated. The highest yield of infective juveniles (IJ) in monoxenic sponge culture system for Sp94-1 and Hi212-2 was 3.52 (± 0.45) × 105 and 7.08 (± 0.11) × 105 IJ g−1, respectively. The optimum storage temperature was 25°C for Sp94-1 and 14°C for Hi212-2. Sp94-1 showed greater tolerance to heat exposure and UV radiation, while S. carpocapsae All, a commercial strain, was more resistant to osmotic pressure, desiccation, cold treatment and hypoxia than the other tested isolates. Hi212-2 suppressed the Phyllotreta striolata larvae when applied at 1.5 × 109 IJ ha−1 or higher concentrations, while Sp94-1 suppressed the P. striolata larvae only when applied at 4.5 × 109 IJ ha−1. Our study indicates the possibility of commercialisation of the EPN isolates, and further confirms their efficacy against the P. striolata larvae in the field.

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